Thanks to this thread, I took my 32 month old iPhone 5 with a separating screen to the Apple Store today for a Genius bar appointment. I assumed they would tell me it would require a screen or battery replacement and that it would not be covered under warranty.
The second the tech saw the screen, he said he knew it was a swollen battery that was causing the screen to separate. He explained that the enlarged battery places pressure on the back of the screen, causing it to shimmer with different colors when you press on the screen. He said that because it is a battery defect, it is covered for 36 months with the iPhone 5, and they don't attempt to repair them due to the potential for battery leakage and other damage it may have caused.
So I walked out with a brand new iPhone 5. Free replacement.